Javascript using prototype how can I set the value of “this” for a number?

Question

So if we can get past the \"should you?\" question ... does anyone know how to set the value of an integer in prototype?

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Answer 1

JavaScript has both number primitives and Number objects. Number primitives are immutable (like all primitives in JavaScript). The numeric value of a Number object is also immutable. So your add method can only return the updated value. You can create your own number-like object, of course, with a mutable value.

Details about number immutability and your own number object in this other answer (didn't realize that question was a duplicate when answering it).

Answer 2

Number.prototype.add = function(num){
  var newVal = this.valueOf() + num;
  this.valueOf(newVal);
  return newVal;
}

var rad = new Number(4001.23);
document.write(rad.add(10) + '<br/>' + rad);

Answer 3

Essentially you cant, Numbers, Booleans and Strings are immutable